(a) Technical Field
The present invention relates to a sound absorbing and insulating material with superior moldability and appearance and a method for manufacturing the same, more particularly to a sound absorbing and insulating material consisting of an inner sound absorbing and insulating layer 1 formed of a first nonwoven fabric mainly formed of a heat-resistant fiber and a binder uniformly distributed inside the first nonwoven fabric and maintaining the three-dimensional structure inside the first nonwoven fabric and an outer sound absorbing and insulating layer 2′, 2″ formed of a second nonwoven fabric mainly formed of a heat-resistant fiber, wherein the outer sound absorbing and insulating layer is stacked on one or both sides of the inner sound absorbing and insulating layer, and a method for manufacturing the same. The sound absorbing and insulating material of the present invention has superior sound-absorbing property, flame retardancy, heat resistance, heat-insulating property and high-temperature moldability. In addition, there is no concern of deterioration of surface appearance caused by leakage of the binder due to the presence of the outer sound absorbing and insulating layer.
(b) Background Art
Noise, as an unwanted side effect of industrial development, causes gradually more damages. A variety of measures are taken to prevent noise. As a way of such noise prevention, researches for developing new sound absorbing and insulating materials capable of arresting, absorbing or insulating sound are conducted in various ways.
Representative industrial sectors requiring sound absorbing and insulating materials include electric appliances such as an air conditioner, a refrigerator, a washing machine, a lawn mower and the like, transportation such as an automobile, a ship, an airplane and the like, construction materials such as a wall material, a flooring material and the like, and so forth. The sound absorbing and insulating material is required in other various industrial fields, too. In general, the sound absorbing and insulating materials used in industries require, in addition to good sound-absorbing property, reduced weight, flame retardancy, heat resistance and heat-insulating property, depending on particular applications. Especially, flame retardancy and heat resistance may be further required for sound absorbing and insulating materials used in engines, exhaust systems and the like maintained at high temperatures of 200° C. or above. At present, an aramid fiber is gaining attentions for sound absorbing and insulating materials having superior heat resistance.
In addition, in order to provide functionalities such as flame retardancy, water repellency and the like to a sound absorbing and insulating material, many sound absorbing materials wherein a nonwoven fabric containing aramid fibers and a functional skin material are stacked have been developed.
For example, Korean Patent Publication No. 2007-0033310 discloses a flame-retardant sound absorbing material wherein a nonwoven fabric layer in which a heat-resistant short aramid fiber and a short thermoplastic polyester fiber are bridged and a skin material layer formed of a wetlaid nonwoven fabric consisting of a short aramid fiber are stacked.
And, Japanese Patent Publication No. 2007-0039826 discloses a water-repellent sound absorbing material wherein a nonwoven fabric layer of a heat-resistant short aramid fiber or a blend of a short aramid fiber and a short thermoplastic polyester fiber and a skin material layer treated with a water repellent are stacked.
And, Japanese Patent Publication No. 2007-0138953 discloses a heat-resistant sound absorbing material wherein a nonwoven fabric layer consisting of a heat-resistant aramid fiber and a skin material layer formed of a fiber sheet containing a heat-resistant aramid fiber are stacked.
Since the sound absorbing materials described above have a structure wherein a skin material layer is laminated on one side of a nonwoven fabric to provide functionalities such as flame retardancy, water repellency and the like, a hot pressing process for integrating the nonwoven fabric layer and the skin material layer is necessary. Consequently, the overall process is complicated and troublesome and a flame retardant, a water repellent and the like included as additives may cause production of toxic gases as a result of combustion during the hot pressing process. In addition, deformation of the internal structure of the nonwoven fabric that may occur during the hot pressing process can lead to deterioration of sound-absorbing property.